Surgeons are constantly striving to develop advanced surgical techniques resulting in the need for advanced surgical devices and instruments required to perform such techniques. Recent advances in the surgical field are increasingly related to surgical procedures which are less invasive and reduce the overall trauma to the patient. To illustrate, in a conventional CABG procedure it has been common practice for surgeons to perform a sternotomy to expose the body cavity in the thoracic region. To this end, a surgeon makes a long incision down the middle of a patient's chest, saws through the length of the sternum and spreads the two halves of the sternum apart. Retractors then are employed to provide access to the vessels where an anastomosis will be performed. The CABG procedure is further complicated by the need to stop the beating of the heart by means of cardioplegia and to attach the patient to a cardiopulmonary bypass (CPB) machine to continue the circulation of oxygenated blood to the rest of the body while the graft is sewn in place.
To create a pedicled bypass graft, the surgeon dissects a sufficient length of the artery from its connective tissue, then transects the artery, and connects the transected end to a diseased target coronary artery distal to an obstruction, while leaving the other end of the dissected artery attached to the arterial supply, thus restoring blood perfusion to the heart.
The internal mammary arteries (IMAs), left (LIMA) and right (RIMA), are particularly desirable for use as pedicled bypass grafts as they are conveniently located, have diameters and blood flow volumes that are comparable to those of coronary arteries, and in practice typically have patency rates superior to other grafts such as saphenous veins from the patient's leg. Extending from the subclavian arteries near the neck to the diaphragm and running along the backside of the ribs adjacent the sternum, the IMAs deliver blood to the musculature of the chest wall. The LIMA is typically used as an arterial source for target locations on the left anterior descending coronary artery (LAD), the diagonal coronary artery (Dx), the circumflex artery (Cx), the obtuse marginal artery, and the ramus intermedius coronary artery. The RIMA is typically used for connection to all of the same target locations, as well as the right coronary artery (RCA) and the posterior descending artery.
Use of either IMA as a bypass graft first involves harvesting the IMA free from the inside chest wall. In conventional CABG approaches, access to the IMA is obtained through a sternotomy or major thoracotomy incision (involving sawing through one or more ribs) through the chest. Harvesting of the IMAs is accomplished with relative ease due to the working space made available by the sternotomy or major thoracotomy.
An IMA is detached from its connective tissue until there is sufficient slack in the IMA to allow the distal end thereof to be attached to the target vessel such as the left anterior descending coronary artery (LAD). The sternotomy incision provides the surgeon with ready access to the IMA since it is exposed by the spreading of the sternum. The IMA thus may be transected at its distal end and detached from the connective tissues in its native location in the sternum region, while still attached at its proximal end to its arterial supply, using the usual surgical instruments such as electrosurgical pencils, scissors, forceps, etc.
The CABG procedure would be improved if surgeons could avoid the need for arresting the heart, thereby eliminating the need to connect the patient to a cardiopulmonary bypass machine to sustain the patient's life. To this end, recent developments lend themselves to CABG procedures using surgical techniques which enable surgeons to perform the procedure while the heart is beating. This eliminates the need for the lengthy and traumatic cardiopulmonary bypass procedure, cardioplegia is unnecessary, the overall surgery is much less invasive and traumatic, and patient recovery time and costs are reduced. Recently, progress has been made in advancing minimally invasive surgical techniques, particularly in cardiothoracic surgery, which eliminates the need for a sternotomy or major thoracotomy. Access to the heart with these minimally invasive techniques is obtained through one very small surgical incision (such as a minimal thoracotomy) or through several percutaneous cannulas known as trocars positioned intercostally in the thoracic cavity of the patient. Visualization of the operative area may be facilitated by thoracoscopes which typically consist of a video camera configured for introduction through a small incision or trocar to allow observation of the target area on a video monitor.
With the advent of these minimally invasive techniques, harvesting the IMA has become more complex and difficult due to a restricted work space and access, and to reduced visualization of the IMA. The procedure of detaching the IMA likewise must be performed through the minimal thoracotomy. Surgeons presently perform the procedure of detaching the IMA from its native location with the aid of the usual instruments such as the electrosurgical pencils, scissors and forceps of previous mention. These instruments are not specially designed for use in less invasive procedures and do not facilitate the desired gentle handling of the IMA as it is detached from the surrounding connective tissues to provide the bypass graft for the CABG procedure. The harvesting procedure itself may actually be lengthened and the trauma to the vessel potentially increased by the less invasive techniques, in part because a number of tools must be introduced and exchanged through the restricted incision(s). This is a concern as a high degree of precision is required when harvesting a bypass vessel to avoid injury (such as over cutting or cauterizing) to the vessel which may in turn lead to increased rates of occlusion in the vessel in the months and years after the procedure.
Although low-profile micro-surgical instruments are readily available for some procedures, such has not been the case for harvesting the IMA and other similarly situated arteries in minimally invasive CABG procedures. Surgical instruments designed for laparoscopic and other minimally invasive applications are not generally suitable for performing minimally invasive CABG. Most laparoscopic procedures, for example, target body structures which are quite large in comparison to coronary vessels, and do not require the high degree of precision required in a CABG procedure. Accordingly, laparoscopic instruments generally provide only limited angular orientation, making them unsuitable for harvesting of the IMA and other similarly situated arteries through a minimal thoracotomy or an intercostal puncture site.
Typically, an electrosurgical tool (often called a "Bovie") similar to that described in U.S. Pat. No. 5,013,312 is used to free a length of the IMA by incising the endothoracic fascia and severing the side branch vessels to free the IMA. The use of such electrosurgical devices is well known in the art and can be crucial in controlling bleeding during harvesting of the IMA. Such devices are typically in the form of scalpels, forceps, and scissors, and employ at least one conductive electrode connected thereto. For example, a bipolar electrosurgical instrument comprising a fork-shaped configuration is described in U.S. Pat. No. 4,671,274. This instrument combines the functions of tissue manipulation and electrocautery, and finds application for control of bleeding during the transection of blood vessels; however, it involves separate hinged jaws and cannot provide an adequate range of angular motion through a minimally invasive thoracotomy.
Despite the use of an electrosurgical tool, because initial cauterization may be applied over too short a length of a vessel or side branch to be complete, it is common practice to apply ligatures or surgical clips to control bleeding before complete coagulation is effected. Applying ligatures or clips can be time-consuming. In addition, if clips are accidentally loosened and dropped inside the patient's body cavity, there can be serious complications and additional expenditure of time in the procedure.
When an electrosurgical tool is used in simultaneous conjunction with other instruments that are not electrically insulated, there is a serious risk of accidental electric short-circuiting or arcing due to contact or close proximity. This can lead to traumatic electric shock to the patient or the surgeon, damage to an instrument, disruption of the procedure, or over or under cutting or cauterization, which can adversely affect the control of bleeding or the integrity and patency of the graft vessel.
Accordingly, it would be highly desirable when performing a detachment, or "take-down" procedure on the IMA, to provide a specialized instrument which allows the surgeon a greater range of visibility and angular motion to harvest an intact and undamaged length of vessel more rapidly and gently with fewer instruments obstructing the operating field and with minimal risk of accidental electric shock, while the tissues and side branch vessels are being dissected with the aid of a surgical knife or scissors. It would further be desirable to reduce or eliminate the need for surgical clips or sutures in the IMA harvest procedure.